In Brewer's Dictionary of Rogues, Villains and Eccentrics, the late William Donaldson credited Simon Dee with having given his name to a modern phenomenon called 'Simon Dee Syndrome', defined as a condition suffered by those who are "better remembered for having been forgotten than they would be if they were still remembered, which indeed they are, but only for having been forgotten, which they are not."

Clearly, the species of celebrity that Donaldson had in mind were bears of little brain -- disc jockeys, television presenters and so on -- and, at first glance, it seems unfair to apply this to a distinguished playwright like Peter Nichols. True, he has never repeated the success of his theatrical debut, A Day in the Death of Joe Egg (1967), but he has written a number of other award-winning plays, including The National Health (1969), Privates on Parade (1977) and Passion Play (1981). If asked to come up with a list of Britain's greatest living playwrights, most drama critics would include Nichols in their top ten.

Yet in the past 25 years or so he has emerged as the theatre's pre-eminent Grumpy Old Man, a field in which there is no shortage of Victor Meldrews. It isn't simply that he has difficulty getting his new work performed. After all, that's an honour he shares with virtually every playwright of his generation. It's more to do with the fact that he can't be bothered to conceal his anger. In 1993, after an abortive attempt to persuade Richard Eyre to stage a couple of his plays at the National, he published a poem entitled The Rime of the Ancient Dramatist in which he depicted himself as an embittered drunk berating Eyre at a party. Eyre, who was the National's director at the time, was reported to be far from happy.

It is precisely this type of reckless behaviour -- acting without a thought to his own self-interest -- that has earned Nichols his status as the best unproduced playwright of our age.

"I don't seem to have handled my career very well," he told The New York Times in 2003. "I've had the impression that stage doors are closed to me. It may be a paranoid delusion, but I think I'm a bit blacklisted."

In person, Nichols is a far cry from the bilious figure I'd imagined. Most of his work is autobiographical to a greater or lesser degree and I was expecting him to be like the central character in A Piece of My Mind (1987), his play about a neglected dramatist. In fact, he's a mild-mannered, congenial fellow -- a little chilly at first, perhaps, but soon regaling me with note perfect impressions of Harold Pinter, John Osborne and Laurence Oliver, whom he dubbed "Sir Larynx Delivery" in his first volume of Diaries (2000). He's particularly good-humoured, given that my appearance on his doorstep at 3.30pm in the afternoon is a complete -- and no doubt unwelcome -- surprise.

"I was expecting to do this by phone," he says, ushering me into his sitting room.

It would be wrong to say he lives in some style, but his Belsize Park maisonette, which he shares with his wife Thelma, is not exactly a home for distressed gentlefolk. It's elegant and well-furnished, precisely the kind of eyrie you'd associate with a successful man of letters.

"My father advised me to take out a pension and thank God I followed his advice," he says. "That's what I'm living on now."

Richard George Nichols was a Bristol-based salesman for the Cooperative Society and, if his depiction in Forget-Me-Not Lane (1971) is anything to go by, a fairly buttoned-up, puritanical man. Nevertheless, he often went to the theatre because his brother, who was a theatrical agent, had charged him with keeping a look out for promising performers. Some of Nichols's earliest memories are of sitting in the Hippodrome or the Old Vic, squirming with embarrassment as his father shouted out "ladies present" in an attempt to get various potty-mouthed comedians to leave the stage.

He made no effort to go to university in spite of the sacrifices his parents made to get him a decent education and, instead, was conscripted into the Royal Air Force. Posted to an entertainment corps in Singapore, he found himself in the same troupe as Kenneth Williams, Stanley Baxter and John Schlesinger and it was here, he says, that his real education began. This experience formed the basis of Privates on Parade, an account of "the British Army's Song-and-Dance Unit in South-East Asia" that went on to become his second most successful play. Not only was it a West End hit when first done at the Aldwych in 1977, but it was subsequently turned into a film starring John Cleese and, more recently, revived by Michael Grandage at the Donmar Warehouse. This was in 2002 and followed hot on the heels of Grandage's critically-acclaimed revival of Passion Play. For a brief moment it looked as though Nichols was back in vogue, thanks to Grandage's patronage, but it wasn't to be.

"We did those two, but that's about as far as it went," he says.

After being demobbed, Nichols joined the Bristol Old Vic Theatre School and, much to his father's consternation, pursued a career as an actor. However, when it became clear that he couldn't earn a living treading the boards he enlisted at a teacher training college.

"I appeared as Dracula at the Theatre Royal, Glasgow," he says. "The notice in the following day's paper was headlined: 'Count Dracula: No Longer So Fearsome'."

Unwilling to abandon his dream of a life in the theatre, Nichols entered a BBC playwriting competition -- and, to his amazement, won. "I don't think I'd ever seen a television play before," he says. After Walk on the Grass (1959) came Promenade (1960), another TV play, and he was confident enough to give up teaching and concentrate on writing full time. By now he was married to Thelma, a childhood friend, and their first daughter, Abigail, was born in 1960. She was severely brain-damaged and had to be hospitalized from the age of three onwards, a tragedy that inspired A Day in the Death of Joe Egg seven years later. In the interim he continued to eke out a living as a writer, with his most conspicuous success being Catch Us If You Can, a caper film about the Dave Clark Five directed by John Boorman.

"Boorman said 'Out of this I'm going to get a Hollywood contract and you're going to get time to a stage play' and he was right," says Nichols. "He went on to direct Point Blank and I wrote Joe Egg."

Nichols describes the success of Joe Egg as "one of those Cinderella things" -- and it was the Australian director Michael Blakemore, then an associate at the Glasgow Citizens' Theatre, who acted as his Fairy Godmother. He and Blakemore met through the Stockpot -- the Ivy for resting actors -- and shortly after he arrived in Glasgow the ambitious Antipodean asked Nichols if he had any plays in his desk drawer. Nichols sent him the newly-minted Joe Egg and the subsequent production was everything he hoped for.

[This quote is new.] "I've cried about three times in my adult life -- and one of them was at a run-through of that first production of Joe Egg," he says. "I must say, that was a good moment."

In spite of Blakemore's brio as a director, the play might not have become such an international hit if it hadn't been for Blakemore's talent as a promoter as well. After a rave review appeared in the Scottish edition of The Guardian, Blakemore rang the editor and persuaded him to run the same notice in the national edition -- and it was only then that the production started to attract serious attention. It transferred to the West End and then opened on Broadway with Albert Finney in the lead.

"When young playwrights ask for advice I always say 'get a friend at court'," he says, by which he means someone worldly and well connected. Michael Blakemore was Nichols's "friend at court" -- or, at least, he was until they quarrelled in 1973. [This quote is new.] "He felt I didn't give him enough credit for what he did for my stuff," says Nichols, "and he's probably right."

Still, it wasn't just Blakemore's involvement that accounted for the phenomenal success of Joe Egg. For one thing, it was very funny. At the time, Nichols was an admirer of the improvised comedy routines of Mike Nichols and Elaine May and he tried to incorporate some of the same offbeat humour into the play. For another, it dealt openly with a subject -- the birth of a mentally handicapped child -- that most people preferred to sweep under the carpet. To insist that the figure of the child be wheeled on to the stage, where she was in full view of the audience, was genuinely ground-breaking. In theatrical terms, Nichols seemed like the Holy Grail: a dazzlingly gifted playwright who was willing to take on a difficult subject in a way that was accessible to the mainstream audience.

[This quote is new.] "We bought a house in Greenwich with the royalties from Joe Egg's Broadway run," says Nichols -- though even when describing the play's commercial success he's reluctant to blow his own trumpet. "We called the house Albert Hall. It's that old bugger celebrity and Albert Finney was a huge star at the time. I almost felt people weren't seeing the play."

After Joe Egg, Nichols had 15 good years, enjoying a run of theatrical successes that only came to an end with the failure of Poppy (1982), a musical comedy about the Opium Wars. Highlights from this period include The National Health, his first play at the Olivier-run Old Vic; Forget-Me-Not Lane, which Blakemore directed at the Greenwich Theatre; Chez Nous (1973); and The Freeway (1974). It's a mark of how well regarded he was in this period that he won the Evening Standard Best Play Award four times.

In the course of working on Poppy, Nichols fell out with Terry Hands, the director, who called him "a wayward, curiously self-destructive genius". Nichols made the mistake of talking about the dispute in the press and after the resulting furore had died down he vowed to give up playwriting altogether. Needless to say, he didn't stick to this resolution. After publishing his autobiography, Feeling You're Behind (1984), he returned to the stage with A Piece of My Mind which enjoyed a brief run at the Apollo in a production that Nichols himself directed. It got mixed reviews, confirming Nichols's view that he'd fallen out of favour with the metropolitan elite.

"Another piece of advice I would give young writers is not to have a character called The Critic who lives in a toilet in your play," he told a newspaper interviewer in 2000.

Nichols kept on writing plays, but he couldn't persuade anyone to put them on. After A Piece of My Mind flopped in 1987, he didn't have another new one produced until 1995, when he got Blue Murder on at the Quakers Friars' Theatre in Bristol. Since then, his only other new play to see the light of day has been So Long Life which enjoyed a brief run at the Bath Theatre Royal in 2001.

[This quote is new.] "I wrote an episode of Inspector Morse," he says, "but I'm so uninterested in plot that when it's on I can hardly work out who did the murder."

There have been revivals, of course -- most notably a production of Joe Egg directed by Lawrence Boswell that started out at the King's Head and ended up on Broadway -- but nothing he's written since Passion Play has enjoyed any real success.

This is reflected in the rather muted celebrations of his forthcoming birthday on July 31. A revival of Forget-Me-Not Lane is currently playing in Scarborough and he's due to be interviewed by Michael Grandage on stage at the National on August 3 -- but that's it.

"Forget-Me-Not Lane is the only play of mine which is being done this year in spite of it being my 80th," he says.

Why is this? The most uncharitable explanation is that he was over-rated during his heyday. If, as George Orwell said, the only true test of literary merit is survival, then there's no such thing as an unjustly forgotten writer. Perhaps Nichols's plays are precisely where they deserve to be -- consigned to the remainder bin of history.

To my mind, that's simply wrong. I worked as The Spectator's drama critic for five years and the revivals I saw of Privates on Parade and A Day in the Death of Joe Egg were among the most stimulating and enjoyable evenings I spent in the theatre in that period.

Much more likely is that Nichols's plays are far too accessible. Contemporary British theatre -- particularly the subsidized theatre -- is a directors' medium and those at the top of the field prefer plays that are cryptic and opaque so they can impose their own interpretations on them. This accounts for the fact that Pinter and Beckett are as fashionable as they've always been, while Coward and Rattigan have fallen from favour.

"I've been accused of being too entertaining," says Nichols. "One critic complained I had too many jokes in Privates on Parade and then went on to repeat about 200 of them."

Nichols also suffers from an almost chronic lack of guile when it comes to advancing his own cause. [This quote is new.] "A producer once tried to raise the money for a Broadway production of Passion Play and he got me in to speak to a group of potential investors," he says. "Far from pitching it, I talked it down. I said, 'You'd be crazy to invest in this play.'"

He claims that this self-deprecation is an unwanted character flaw, but, talking to him, you get the impression that it's rooted in a moral dislike of self-promotion -- the legacy of his father's Puritanism, perhaps. All the more reason, then, that he should ally himself with those who are willing to fight on his behalf -- but his visceral disapproval of all types of self-interested behaviour appears to extend to the formation of such useful "friendships".

There's a very telling footnote in his Diaries, added in 1999, in which he reflects on how foolish he was to quarrell with Michael Blakemore: "Never having much relish or talent for what Kenneth Williams always called 'the business end' or 'the suck-off antics', I needed someone in my corner who enjoyed pacing the corridors of power. Anyone who lacks this aptitude should find a partner who has it, a lesson painfully learnt by me over the last fifteen years. The work itself comes at best a poor second to strategy. The wastage of gifted people in various trades is due more to this than any falling-off in achievement."

As I'm preparing to leave Nichols's flat, I ask him if it might be possible to see his workroom -- the place where he has toiled, largely in vain, for the past 25 years. With some reluctance, he leads me up the stairs, passing various posters on the way, all advertising old productions of his plays. When we arrive in the brightly lit room he stands off to one side.

"These are mostly unproduced plays," he says, gesturing towards a bookshelf heaving with bound manuscripts. I can make out a couple of titles: Beasts of England, A Better Mousetrap. A binder bears the legend "Unpublished Novels".

"Theatrical fame is terribly fickle," he says with a rueful smile.

"Is it better to have had fame and lost it than never to have had it at all?" I ask -- then immediately curse myself for being so crass and insensitive.

"Better to have loved and lost," he says distractedly, leaving the sentence unfinished.

Then he snaps back into focus.

"I don't care about fame. What I want is to get the stuff on. Whenever I see all those giveaway shows I always think, 'Oh, just for one of those millions.' I'd love to have my own theatre, like Alan Ayckbourn. All those plays up on my shelf -- at least they would have been seen."

Who knows, perhaps they will be one day. Survival may be the best test of literary merit, but what Orwell had in mind was a period of several hundred years, not a couple of decades. When it comes to Peter Nichols, the verdict of posterity may be very different from that of the current gaggle of theatrical gatekeepers.